1. Technical Field
The embodiments of the present invention relate to a semiconductor integrated device, and more particularly, to a resistive memory device, a method of fabricating the same, and a memory apparatus and a data processing system having the same.
2. Related Art
Dynamic Random Access Memories (DRAMs) operate at high speed, but the DRAMs are volatile. Flash memories are highly integrated and nonvolatile, but the flash memories may not guarantee operation speed equivalent to DRAM operation speed.
Studies on memory devices having advantages of the DRAMs and flash memories have been actively progressed, and resistive memory devices that are nonvolatile and operate at a high speed have been suggested.
The resistive memory devices are a memory device using a variable resistive material, which switches at least two resistance states by rapid resistance change based on an applied voltage. There are phase-change RAMs (PCRAMs) and resistive RAMS (ReRAMs) memory devices as the resistive memory devices.
The PCRAMs store data by changing a crystalline state of the variable resistive material with current applied to a heating electrode. The PCRAMs have advantages of a nonvolatile property, high operation speed, stability, unnecessity of an erase operation, endurance, and support for access in units of bytes.
The PCRAMs have to be designed to support a multi-level cell (MLC) structure to obtain large capacity and high integration. The PCRAMs having the MLC structure, which have been studied until recently, are implanted using a method of controlling a pulse applied to memory cells having the same structure as a single-level cell (SLC).
That is, the current PCRAMs have to accurately control a pulse type applied to implement the MLC, and this is because a set/reset state of data becomes transited depending on crystallization of a phase-change material. When the property of the phase-change material is changed by repetitive use of the PCRAMs, undesired data is written, and thus, there are limitations to implement MLC through the same structure as SLC.